1. Field of the Invention
The present invention relates to a semiconductor device and a method for manufacturing the same. The present invention particularly relates to a semiconductor device having a semiconductor chip whose back is exposed, and a method for manufacturing the same.
This application is counterpart of Japanese patent applications, Serial Number 250482/2001, filed Aug. 21, 2001, the subject matter of which is incorporated herein by reference.
2. Description of the Related Art
With size reductions in portable devices, there has been a demand for a reduction in the size of semiconductor devices in the portable device. In order to meet such a demand, a semiconductor device called a “Chip Size Package” having outside dimensions approximately identical to those of a semiconductor chip has come along. As one form of the chip size package, there is known a semiconductor device called a “Wafer Level Chip Size Package” or “Wafer Level Chip Scale Package”. In such a wafer level chip size package (hereinafter called “WCSP”), the surface of a semiconductor chip is sealed with a resin, whereas the back (silicon surface) thereof has an exposed structure. In the WCSP, an index mark such as a one pin mark or the like for determining the direction of mounting of the WCSP on a printed circuit board is formed on the back (silicon surface) of the exposed semiconductor chip by marking processing. As the marking processing, may be mentioned, for example, a laser mark system for forming each mark by laser processing.
However, the back (silicon surface) of the semiconductor chip is ground to further thin the thickness of the WCSP and due to reasons such as the difference between the linear expansion coefficient of silicon and that of the printed circuit board. The silicon surface thereof is held in a mirror state. A problem arises in that even if a laser is used to effect marking on the silicon surface held in such a mirror state, the difference between the intensity of light reflected by a location subjected to the marking and the intensity of light reflected by a location free of the marking is small, i.e., the contrast is low, and hence the recognition of each mark falls into difficulties. The difficulty of recognizing the mark means that the automatic mounting or packaging of the WCSP on the printed circuit board by use of an automatic mounting or packaging device provided with an image recognizer is also difficult. Further, the difficulty of recognizing the mark means that a visual inspecting device with an image recognizer encounters difficulties in determining whether the WCSP is placed in a proper orientation upon a visual inspection done after the packaging of the WCSP on the printed circuit board.
Thus there has been a demand for a semiconductor device capable of easily determining the direction of packaging.